Messenger RNA turnover has long been recognized to play a key role in controlling gene expression in all organisms. The long-term goal of this research project is to understand the basic principles that govern mRNA degradation in bacterial cells. The immediate objectives are to elucidate the specificity and mechanism of 5'-end-dependent RNA degradation in Escherichia coli and Bacillus subtilis by investigating the proteins that are central to this regulatory pathway and the transcripts that they target. Achievin these objectives will require not only the use of standard molecular biological, biochemical, and genetic methods but also the development of new low- and high-throughput techniques for analyzing the 5' phosphorylation state of individual transcripts and for using genetic screening to identify pertinent clones and mutants. The knowledge gained from these studies will provide important insights into a fundamental aspect of gene regulation that can play a key role in bacterial pathogenesis.